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Strength of Ternary Blended Cement Concrete Containing Oil…
Table 2. Compressive strength of blended OPC-OPBA-PLA cement
concrete at 28-90 days of curing
OPC Compressive Strength (N/mm 2 ) for
Plus 0%
Poz.
5%
Poz.
10%
Poz.
15%
Poz.
20%
Poz.
25%
Poz.
Strength at 28 days
OPBA 24.00 23.80 22.10 20.40 18.20 16.30
PLA 24.00 24.70 23.00 21.20 19.00 17.20
OPBA 24.00 24.30 22.60 20.70 18.50 16.90
& PLA
Strength at 50 days
OPBA 24.50 25.20 24.40 22.60 20.50 19.30
PLA 24.50 26.00 25.20 23.10 21.20 20.00
OPBA 24.50 25.70 24.80 23.00 20.90 19.60
& PLA
Strength at 90 days
OPBA 24.60 26.70 25.80 25.00 23.40 21.80
PLA 24.60 27.30 26.20 25.30 24.00 23.00
OPBA
& PLA
24.60 27.00 25.90 25.10 23.60 22.10
It can be seen in tables 1 and 2 that 100% OPC concrete (the control) strength increased steadily till the age of
about 28 days, after which it increased only gradually until the age of about 90 days. Table 1 shows the low strength of OPC-
OPBA-PLA ternary blended cement concrete relative to the strength of the control concrete at early ages of 3 to 21 days,
especially at 3-14 days. The poor early strength gets more pronounced with increase in percentage replacement of OPC with
OPBA-PLA combination as shown in table 2. This very low early strength could be due to the fact that pozzolanic reaction
was not yet appreciable at early ages. The pozzolanic reaction set in after some days and increased with days of
curing/hydration such that the strength of blended cement concrete increased more and more with age than that of the
control. Table 1 clearly shows that very high strength could be achieved for OPC-OPBA-PLA ternary blended cement
concrete with 10 to 15% replacement of OPC with pozzolans at 50 to 90 days of curing.
Tables 1 and 2 also show that the strength values of OPC-OPBA binary blended cement concrete are higher than
those of OPC-PLA binary blended cement concrete with5-10% OPC replacement at 3-21 days of hydration. Compressive
strength values of OPC-PLA binary blended cement concretegets higher than those of OPC-OPBA binary blended cement
concrete with15-25% OPC replacement at 3-21 days and at 28-90 days for all percentage replacements of OPC with
pozzolan. The higher strength of OPC-OPBA binary blended cement concrete relative to that of OPC-PLA binary blended
cement concreteat the earlier days of hydration shows that the pozzolanic reaction with OPBA sets in faster than that with
PLA. Also, the fact that the strength of OPC-PLA binary blended cement concretegets higher than that of OPC-OPBA binary
blended cement concrete at later days of hydration would suggest that PLA contains more quantity of non-amorphous silica
than does OPBA. The strength value of OPC-OPBA-PLA ternary blended cement concrete consistently lies in-between the
values for OPC-OPBA and OPC-PLA binary blended cement concretes for all percentage replacements and curing ages.
This suggests that a disproportionate blending of the two pozzolans should be in favour of OPBA for optimization of the
early strength of OPC-OPBA-PLA ternary blended cement concrete and in favour of PLA if the later strength of OPC-
OPBA-PLA ternary blended cement concrete is of greater importance.
IV. CONCLUSIONS
Ternary blended cement concrete produced from blending OPC with equal proportions of OPBA and PLA have
compressive strength values in between those of binary blended OPC-OPBA and OPC-PLA cement concretes for all
percentage replacements of OPC with pozzolansand at all curing ages. Also, the variation of strength for OPC-OPBA-PLA
ternary blended cement concrete is similar to those of OPC-OPBA and OPC-PLA binary blended cement concretes for all
percentage replacements and curing ages. More importantly,the 90-day strengths of OPC-OPBA and OPC-PLAbinary
blended cement concrete as well as that of OPC-OPBA-PLA ternary blended cement concrete are all higher than the control
values for 5-15% replacement of OPC with pozzolans and close to the control values for 20-25% replacement. The
implication of this is that very high strength values of OPC-OPBA and OPC-PLA binary blended cement concrete as well as
OPC-OPBA-PLA ternary blended cement concrete could be obtained if high target strength is intentionally designed for and
good quality control is applied such as the quality control measures used in producing 100% OPC (control) concrete with
high strength values. Thus, OPC-OPBA-PLA ternary blended cement concrete could be used for various civil engineering
and building works, especially where early strength is not a major requirement.
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